This invention relates to the field of organic synthesis, more particularly to a process for the preparation of a bicyclic decalin ketone, viz. perhydro-5,5,8a-trimethyl-2-naphthalenone. This ketone is a useful starting material in the synthesis of perhydro-5,5,8a-trimethyl-2-naphthalenyl acetate [Polywood .RTM.; trademark of Firmenich SA, Geneva, Switzerland], a fragrance speciality well appreciated for its tenacious and elegant woody note. The ketone itself possesses a strong woody and ambery odor.
Owing to its structure, it may occur under two isomeric forms of formula ##STR8## their reduction followed by acetylation yielding the desired acetate.
In actual experience it has become apparent that, among the possible isomers, perhydro-5,5,8a.alpha.-trimethyl-2.alpha.-trans-naphthalenyl acetate is the compound which possesses the most interesting olfactive characters, isomer 2.beta. developing instead a note which, though still woody and ambery, is less rich than the 2.alpha. isomer.
French patent 15 93 814 discloses a method for the preparation of ketones (Ia, b) which method is based on the oxidation of a decalin carbinol obtained as follows: ##STR9##
On account of the above, our efforts were directed to the preparation of perhydro-5,5,8a-trimethyl-2-naphthalenone in its trans isomeric form.
The present invention provides a solution to this problem.